A brief history of biological, psychological, functional, and philosophical theorizing on how learning and memory work in the human mind, by New York Times editor Johnson (Machinery of the Mind, 1986). In The Memory Palace of Matteo Ricci (1984), Jonathan Spence described a memory system that employs rooms in an imaginary palace to enclose desired memories. Cognitive science itself is comparable to an architectural structure, Johnson suggests, with philosophers inhabiting the attic, computer scientists and psychologists on the main floors, and the ""wetware"" folks--the neurobiologists--mucking around in the basement. Beginning at the bottom, Johnson outlines the progress made through persistent experimentation with snails, slivers of human brains, and quick-blended neuronal soups to come up with memory models based on synapses, receptors, and enzymes in the brain. Moving upstairs, he recounts tales of computer scientists who have skipped the problem of how neurons work to concentrate on mimicking the results through neural nets and artificial intelligence. Finally, Johnson visits the philosophers' drafty rooms, where he reports the rumor that philosophy itself may soon become obsolete in the face of the scientific process. ""One of the most difficult things about neurobiology is learning to live with ambiguity,"" sums up biologist Gary Lynch. What's true in the basement holds true in the rest of the house--and for the reader as well. Meanwhile, portraits of passionate memory-researchers--including physicist Leon Cooper, artificial-intelligence expert Marvin Minsky, and philosopher Patricia Church-land--liven up the sometimes tedious discourse.